Thomas is a tall teenager with pale skin, straight light blond hair, and light blue eyes. Thomas's civilian attire consists of a dark green v-neck T-shirt, white pants and brown shoes with black soles.
His DATS uniform consists of a dark blue-and-white half-sleeve jacket with two yellow upside down triangle marks on the chest, a blue jumpsuit with a partially white collar underneath, a light grey belt, and white and dark blue knee-high boots.
After he returns from the Digital World and has his memory erased, he begins wearing a white short-sleeved button-up shirt under a green unbuttoned vest, as well as a blue tie, dark blue trousers and brown dress shoes with black soles.
Five years later, Thomas's hair is longer at the back, and he has started wearing glasses with silver frames.
Thomas is a boy genius who graduated from the Stockholm Royal University of Science at the age of 13. His abilities are considered elite, even within DATS. He bases his operations on data and theoretical principles, and as such, his personality clashes with Marcus's. Calm and shrewd, he is the exact opposite of Marcus and sees him as a rival. He has an elitist attitude but he gets emotional when thinking of his mother. Thomas's loyal partner is Gaomon, who always addresses him as "sir" and is easily angered when he thinks someone is disrespecting Thomas.
He is fluent in over 170 languages, including DigiCode.
Thomas's mother is Japanese, and his father is a prominent Austrian aristocrat named Franz Norstein. Franz and Thomas' mother met while she was an exchange student in Austria. Thomas lived with his mother in Japan until she was killed in an accident, after which he was taken back to Austria. Thomas also has a younger half sister, Relena, who suffers from a strange disease. While Thomas does not particularly care for his cold and severe father, he does love his sister very much and does whatever he can to protect her.
Thomas returns to Japan to assist DATS in its Digimon containment efforts. Marcus, however, dislikes the fact that Thomas is his squad leader, and challenges him to a boxing match. They both end up with cheek bruises before DemiMeramon start appearing. Thomas' tactics clashed with Marcus' impulsiveness to simply charge in. Marcus managed to fool 3 DemiMeramon to merge into Meramon so he can be punched for a DNA charge. Afterwards, Thomas concludes that Marcus had no plan and they begin arguing until Commander Richard Sampson tells them they will have to be partners to get along.
They were on the verge of defeating Drimogemon but Marcus' stubbornness resulted in the Digimon escaping back into the Digital World. Thomas requested to go there to return Drimogemon to his Digi-egg form before he could bring other Digimon to the real world but was denied. So he did an unauthorized Digital Dive to go after the gopher Digimon. But he and Gaomon got lured into a trap deep beneath the Digital World surface. Marcus and Agumon, who were sent to rescue them, get trapped as well but they laugh at the fact that the "genius" was outsmarted by a gopher. Marcus has them jump on Drimogemon, pulling his hair to direct him to the surface and into an ice prism where he can't drill. But Drimogemon digivolves into Digmon and proves too powerful for them separately, so Thomas suggests they have their partners attack together, which defeats Drimogeon.
When MetalPhantomon manipulates Thomas's mind, it feeds him nightmares from the past. He is forced to relive his mother's death in a horrific accident in which she was killed by a speeding truck. However, the nightmare does not have the entire desired effect on Thomas, and he pulls through, allowing Gaomon to digivolve to MachGaogamon.
He finally obtained the power to Digivolve his partner further, but his Digivice iC was not able to support the uncontrolled enhanced power of his Digisoul and shattered, with the same process happening to both Marcus' and Yoshi's digivices. Soon after, he and his friends managed to repair their iC's and turn them into Digivice Bursts, allowing Gaomon to digivolve to MirageGaogamon.
After the destruction of ElDradimon, Thomas was forced by his father to abandon his friends and side with DATS' greatest enemy Akihiro Kurata, who claimed to have the means to cure Relena. Unfortunately, Kurata had placed a bomb in Relena's necklace to keep Thomas from betraying him. He even had to fight his former comrades, to the anger of Marcus, who accidentally invoked a dark Digi-Soul to fight him, with disastrous consequences. Once Kurata's men were about to perform surgery on Relena to make her a Bio Hybrid Digimon, Thomas and Gaomon knocked out everyone once the necklace was removed. Thomas then betrayed Kurata by activating the charge he had planted inside the device Kurata was using to control Belphemon, and returned to the DATS team to put a stop to the mad scientist.
Around the same time, he confronted his father and revealed that he had only gone to study abroad in order to become a physician and cure Relena where all other doctors had failed. Thomas gets into an argument with his father and tell's him how he hates being a Norstein to his fathers outrage. He remembers how his grandmother hated him for not being born a "true" Norstein, being half-Japanese, an illegitimate child and not having a mother who was an elite member of society. But because of Relena's illness, his grandmother had no choice but to appoint him as the Norstein heir and ordered his father to find him a suitable woman. While protecting the airplane where Relena was located, Thomas fought against LoadKnightmon and unlocked MirageGaogamon's Burst Mode. After that, he rejoined the others and went to find Marcus back in the Digital World, partaking in all of the events leading up to the final battle.
After the defeat of King Drasil, Thomas was forced to realize that the Digimon needed to go back to their own world, and spent one final evening with Gaomon. The next day, he and the others bid the Digimon farewell as they returned home, only to find out that Marcus had tagged along with them as well.
Digimon Xros Wars: Super Digica Taisen
Notes and references
|Digimon Data Squad|
|DATS Members:||Marcus Damon and Agumon | Thomas H. Norstein and Gaomon | Yoshino "Yoshi" Fujieda and Lalamon | Keenan Crier and Falcomon | Miki Kurosaki, Megumi Shirakawa, and PawnChessmon | Richard Sampson and Kudamon | Homer Yushima and Kamemon|
|Antagonists:||SaberLeomon | Gotsumon | Akihiro Kurata and Gizumon | Bio-Hybrids | Belphemon | Argomon | Royal Knights | King Drasil | Tsukasa Kagura|
| Other characters:||Spencer Damon and BanchoLeomon | Sarah Damon | Kristy Damon and Biyomon | Merukimon | Rhythm | Kosaburo Katsura and Biyomon | Yuma Kagura and Renamon | Masaki Nitta | Other characters|
|Relationships:||Marcus Damon | Thomas H. Norstein | Yoshino "Yoshi" Fujieda | Keenan Crier|
|Other media:||Ultimate Power! Activate Burst Mode!! | The Digital World in Imminent Danger! | Digimon World Data Squad | Digimon World DS | Digimon World Dawn and Dusk|
|See also:||Digimon | Digital World | Digimon Natural Ability | Data Link Digivice | Digi-Egg | List of episodes|